1. Field of the Invention
The present invention relates to a liquid crystal display device, and more particularly, to a liquid crystal panel including bypass capacitors for eliminating noise and ripple from signals.
2. Description of the Prior Art
Generally, a liquid crystal display (LCD) controls a light transmissivity of liquid crystal cells in accordance with a video signal, thereby displaying a picture corresponding to the video signal on the liquid crystal panel in which liquid crystal cells are arranged in a matrix pattern. The LCD includes driving integrated circuits(ICs) for driving the liquid crystal cell matrix in the liquid crystal panel, and an electrical signal converting circuit for driving video signals, timing signals and power supply voltage signals to be supplied for the driving ICs. Typically, the driving ICs are manufactured to be an IC chip and the electrical signal converting circuit is manufactured to be a printed circuit board(PCB).
The driving IC chips are electrically connected to a liquid crystal cell matrix in the liquid crystal panel via a conductive film tab. At this time, the driving IC chips are mounted on either the conductive film tab or the surface of the liquid crystal panel. The LCD may be classified as a tab system LCD and a surface mounted system LCD, which is called "Chips On Glass" (COG), in accordance with a position where the driving IC chips are disposed. Further, the PCB is electrically connected to the driving IC chips via a flexible printed circuit film, hereinafter referred simply to as "FPC".
In the LCD, the video signals, the timing signals and the power supply voltage signals to be supplied from the electrical signal converting circuit, via the FPC, to the driving ICs are influenced by a noise and a ripple, and other harmful effects during the transfer of the signals to the driving ICs. In order to minimize the influence caused by the noise and the ripple and other harmful effects, the LCD further comprises bypass capacitors. These bypass capacitors can improve a quality of the picture displayed on the liquid crystal panel by removing a noise and a ripple and other harmful effects from the video signals, the timing signals and the power supply voltage signals.
A conventional LCD constructed in this way is shown in FIG. 1 and includes a liquid crystal panel 10 in which a liquid crystal cell matrix is defined, source driving IC chips 14 for divisionally driving source lines of the liquid crystal cell matrix 12, and gate driving IC chips 16 for divisionally driving gate lines of the liquid crystal cell matrix 12. The source driving IC chips 14 are located along the upper edge of the liquid crystal panel 10 while the gate driving IC chips 16 are located along the left edge of the liquid crystal panel 10. The liquid crystal cell matrix 12 is typically formed to include thin film transistors(TFTs) located between a lower glass substrate and an upper glass substrate (not shown). Further, the LCD includes a PCB 18 for supplying the source driving IC chips 14 and the gate driving IC chips 16 with the video signal, the timing signal and the power supply voltage, and a FPC 20 for electrically connecting the PCB 18 to the source driving IC chips 14 and the gate driving IC chips 16.
The FPC 20 is provided with bypass capacitors 22 which improve a quality of picture produced on the LCD by removing a noise and a ripple and other harmful effects from the video signals, the timing signals and the power supply voltage signals to be transferred into the source driving ICs 14 and the gate driving ICs 16.
Alternatively, the bypass capacitors 22 may be provided on the PCB 18. The PCB 18 is implemented with an electrical signal converting circuit that generates the video signals, the timing signals and the power supply voltage signals to be supplied for the source driving IC chips 14 and the gate driving IC chips 16.
In the conventional LCD, because the FPC is directly connected to the driving IC chips as described above, the FPC has a very complicated configuration. Also, in the conventional LCD, because the bypass capacitors are provided in the FPC or the PCB, the liquid crystal panel module has a considerable thickness.
A so-called "lines on glass(LOG)" system for an LCD, which system simplifies the structure and the manufacturing process of the FPC by providing a part of the wiring in the FPC on the liquid crystal panel, is now commercially available in the market. This LOG system type of LCD simplifies the structure and the manufacturing process and also reduces the manufacturing cost of the FPC and the LCD. In the LOG system type of LCD, however, it is difficult to make a liquid crystal panel module sufficiently thin because the bypass capacitors are provided in the FPC or in the PCB.
In order to provide the significantly thin liquid crystal panel module, a process for mounting the bypass capacitors on the liquid crystal panel was disclosed in a Japanese Laid-open Patent Gazette No. 7-128678. In JP 7-128678, the bypass capacitors were provided by charging a dielectric material between the liquid crystal panel and the driving IC chips. This process has a disadvantage in that, since the charge of the dielectric material requires a certain amount of space between the liquid crystal panel and the driving IC chips, it is not only impossible to provide a reduced thickness of the liquid crystal panel module beyond a specific limit, but also a wiring pattern and a process for forming the same, which pattern is to be arranged on the liquid crystal panel, becomes complicated. Further, the above process has a disadvantage in that the charge of dielectric material requires an additional manufacturing process after the manufacture of the liquid crystal panel, specifically, after the manufacture of the thin film transistors.